Preheat oven to 350 degrees F (175 degrees C).
Beat the butter or margarine with the white and brown sugars until light and fluffy. Blend in the eggs, mixing well.
Mix in the flour, baking soda and salt to the egg mixture. Reserve 1/2 cup of the chopped candy bars for the topping. Stir the remaining candy into the flour mixture. Spread the batter into one 13x9 inch baking pan. Sprinkle the reserved candy on top.
Bake at 350 degrees F (175 degrees C) for 25 to 30 minutes or until lightly browned. Cool in pan on a wire rack then cut into squares.